Many cardiac surgery procedures require the sternum of the patient to be cut longitudinally and the sternal halves, together the adjoining ribs, to be spread apart so as to allow the surgeon to work on the heart. Retractors are used to spread this surgical opening. If the procedure includes treatment of circulatory disorders of the coronary heart vessels, what is known as a bypass operation is carried out. The establishment of what is known as a mammary artery bypass is one of the most common surgical methods. In such bypass operations, a path is created around a section of a narrowed coronary artery. The internal mammary artery (IMA), which is used as the bypass vessel for this purpose, runs along the inside of the thorax. A portion of this artery is dissected free by the surgeon, and the end is sutured to a coronary artery.
Normally the left internal mammary artery (LIMA) is used, but often the right artery (RIMA) is also used. So as to be able to provide the surgeon with sufficient operating space and adequate visibility for this work, a lifting system is needed, which is able to vertically raise and support one half of the cut sternum, together with the adjoining ribs.
A wide variety of systems of this type is known from the prior art. A first type of lifting systems, which are disclosed in the patent specifications EP 0 931 509 B1 or U.S. Pat. No. 6,416,468 B2, for example, is based on a conventional retractor comprising an adaptor device, which is mounted on the retractor and raises the same on one side. In patent specification EP 0 931 509 B1, the raising is implemented by way of a screw having support plates and a thread pivotably attached to the retractor. The lifting system is clamped or screwed to the retractor. According to patent specification U.S. Pat. No. 6,416,468 B2, the screw and the thread are replaced by a detent mechanism; however, the fundamental operating principle is the same. To raise one side of the sternum, the support plate is pressed against the ribs, whereby the side of the sternum on which the lifting system is located is pulled outward.
The second type of lifting systems is very similar and operates with special blades on an otherwise likewise conventional retractor. Instead of using an adapter device, the principle of the above-described raising is achieved by way of a special blade here, which is attached to the retractor frame in an articulated manner, and a spacer element. The spacer element is used to set the distance between the pivoting side of the special blade and the retractor frame, and thus the raising of the corresponding sternal half. Such systems are described in the documents U.S. Pat. No. 5,025,779 A and DE 10 325 393 B3.
Also known are pure mammary artery retractors, which are not used for normal sternal spreading, but only for carrying out the dissection of the mammary artery. Patent specification DE 3 717 915 C2 describes such a retractor, which functions without a separate lifting device. A blade located at a fixed angle with respect to the toothed rack of the retractor is clamped into the sternal half which is not raised, so that the retractor becomes obliquely positioned with respect to the normal thoracic surface of the patient when the sternum is spread by way of the pinion, and the other sternal half is pulled upward by way of special blades designed as claws.
One technique that differs substantially from the three above-described variants is that of raising one sternal half by way of cables or pull rods in conjunction with an external attachment means. This technique can be found in the published prior art U.S. Pat. No. 6,488,621 B1 or U.S. Pat. No. 6,689,053 B1. Here, only the desired sternal half is raised by way of hooks, which are provided on a cable or a pull rod, wherein the tractive force is absorbed by a fastening element, such as a frame or a rod, which is fastened to the side of the operating table, for example.
In all conventional devices of this type, the user, which is to say the surgeon, must be prepared for several drawbacks, which prevent an optimal process on the one hand, and an ideal result of the surgical procedure on the other hand.
The greatest disadvantage are the high forces which arise when the sternum is raised and the adjoining ribs are spread apart, and which are usually distributed to the body of the patient through supporting elements. The sternal half in question becomes exposed in this process, which is to say bent open outward; however, the force required to do so is distributed to the adjoining ribs on the same side of the body. Due to various lever arms, this results in extremely high forces being exerted on the patient. This, in turn, poses a high risk of partial sternal fractures, fractures of the ribs, and damage to neural pathways.
The technique of external attachment forms one exception, since the force required to expose the sternal half is distributed to the attachment system here, and not to the patient. However, this technique does not provide adequate visibility since only vertical raising of one sternal half takes place, and no adequate opening on the horizontal axis is provided. Due to the absence of horizontal forces, it is also not possible to use regular blades here; rather, claw-shaped hooks are needed, which are seated against the sternum in a highly localized manner and can cause substantial fractures. In addition, such systems are very tall above the operating level and consequently interfere with many work flows of the surgical staff.
Another point of criticism is the extremely cumbersome repositioning of the lifting systems to the other side in the case where two mammary arteries (left and right) require consecutive dissection. This repositioning is still relatively simple in devices that are adapted to the retractor; however, an assistant will usually have to help the surgeon. In contrast, retractors comprising special blades must be completely removed from the surgical opening and repositioned, which represents not only an interruption of the surgical process, but also a relatively critical moment since the surgeon no longer has access to the heart when the retractor is removed.
In systems comprising an external fastening rod, which is mounted to the operating table, there is almost no practical way to reposition the system to the other side. The reason behind this is that all regions located vertically below the surgical area are considered non-sterile. A mounting on the operating table will thus be in the non-sterile region and cannot be detached and relocated to another point. Likewise, work steps that must be carried out during surgery in this region, such as loosening a clamped connection, are impermissible.